Patent GB-391134-A (GB)
Title: Improvements in or relating to protective arrangements for sectionalised electric power circuits
IPC: H02H7/26
Filed: 1931-10-15
Abstract: 391,134. Protective cutout arrangements. REYROLLE & CO., Ltd., A., Hebburn-on-Tyne, CLOTHIER, H. W., 3, Jesmond Park. West, Newcastle-on-Tyne, LEESON, B. H., Waverley, Tynemouth, and LEBEN, H., 8, Queen's Walk, Harrow, Middlesex. Oct. 15, 1931, No. 28725. [Class 38 (v).] In a sectionalized power circuit each section is protected independently of the other sections by means of a tripping relay device at each end, the arrangement being such that the tripping of the circuitbreaker at each end is controlled jointly by the operation of the adjacent tripping relay device, and the operation of the tripping relay device at the other end, means being also provided to prevent tripping of the circuit-breakers at both ends when power is flowing into the section at one end, and out at the other. In the arrangement shown in Fig. 3, with a fault in the section A, current flows into the section at both ends, and non-directional tripping relays D<2>, d<2> at the ends operate. These relays D<2>, d<2> are such as described in Specification 391,135, and operate first to close their contacts D<4>, d<4> and then to close their contacts D<5>. d<5>. Stabilizing directional relays C, c are also provided at each end as described in Specification 314,778, [Class 38 (v), Electric switches &c.], and with a fault such as that being considered, these relays remain inoperative. Closure of the contacts D<4>, d<4>, of the relays D<2>, d<2>, therefore produces no effect, but when the contacts D<5>, d<5> are closed, relays E, e are operated to connect batteries J<1>, j<1>, in series in the pilot wire circuit H<5>, H<6>, so that current flows in such a direction that polarized relays F<2>, f<2> operate, but polarized relays G<2>, g<2> remain inoperative. The contacts E<1>, e<1> of the relays E, e having been closed, and the contacts F<3>, f<3> of the relays F<2>, f<2> closing in response to the energization of the relays, the circuits of the tripping coils B<1>, b<1> of the circuit breakers B, b are completed, and the section A is isolated. With a fault external to the section causing a heavy current to pass from the home end B to the remote end b of the section, the relays D<2>, d<2>, c operate. Closure of the contacts d<4> causes, through contacts c<1> of the relay c, energization of a relay l at the remote end. This relay disconnects the battery j<1> and connects a battery k of higher but opposite potential to the circuit of the pilot wires H<5>, H<6>, which circuit is completed by relays e, E energized by the contacts d<5>, D<5> of the relays d<2>, D<2>. The batteries k, j<1> are now connected in opposition in the pilot wire circuit, and current flows in such a direction that polarized relays G<2>, g<2> operate to open the tripping coil circuits of the circuit-breakers, and prevent isolation of the section. If there is a fault in the section A fed only from the home end B, the relay D<2> only operates to energize the relay E, and after a time interval contacts E<2> are closed to complete the tripping circuit of the circuit-breaker B independently of the contacts F<3>. Simplified arrangements in which the tripping relays D, d are directional, and in which three or four pilot wires are necessary, are described with reference to Figs. 1 and 2 (not shown). In Fig. 4 (not shown), pilot wires are dispensed with, and the relays F<2>, G<2>, f<2>, g<2> are replaced by non-polarized relays which receive currents of different frequencies transmitted over different lines of the main system by transmitters at the remote end controlled by the operation of the relays D<2>, d<2>, C, c. The arrangement shown in Fig. 3 can be adapted to an arrangement in which four pilot wires are used, the relays F2, G2, f<2>, g<2> being non-polarized, and only one battery being required at each end. The pilot wires may be borrowed from telephone or similar circuits. Fig. 6 shows the manner in which the relays D, d; corresponding to the relays D2, d2 of Fig. 3, are connected with a three-phase section A<1>, A2, A3. Here the relays D, d are directional in character, and the invention is carried out in a different manner. With an internal fault fed from both ends, relays D, d operate to energize relays E, e which connect relays S, s to the full voltage of batteries J<3>, j<3> so that contacts S<3>, s<3> open and contacts S<1>, S<2>, s<1>, s<2> close. Contacts El, e<1> having been closed, the circuit-breakers are tripped. With an external fault causing a heavy straight-through current from B to b, relays D, c operate. The relay c energizes a relay l which connects the relay S to the battery j<3> through a resistance p to reduce the current so that the contact S<3> opens, but the contacts S<1>, S<2> are not closed. The relay E is operated by the relay D but the tripping circuit of the circuit-breaker B remains open, and although the relay s is fully energized the relay e is not energized and the circuit-breaker b is not tripped. Fig. 7 shows the preferred embodiment of the invention. Here the arrangement is similar to Fig. 3, but the relays F<2>, G<2> and f<2>, g<2> are replaced by single polarized relays U, u respectively, having two sets of contacts. Furthermore, the relays E, U and e, u do not control the tripping circuit directly, but through additional relays V, v, while the time contacts E<2>, e<2> are provided not on the relays E, e but on additional relays X, x, connected in parallel with the relays E, e. In addition the relays L, l have an added function of borrowing the pilot wires from telephone apparatus. The current coils of the relays C, c, and the relays D, d are energized from transformers M<1>, M<2>, M<3> and m<1>, m<2>, m<3>, while the potential coils of the relays C, c are supplied from transformers N, n. The relays C, c have additional normally closed contacts, through which the relays E, e are energized, while one of the elements of each of the relays D, d, i.e. D<10>, d<10>, has additional normally closed contacts D<21>, d<21>, through which the relays L, l are energized if the element of the relays C, c which operates is not the element C7, c<7> corresponding to the elements D<10>, d<10>. In this way the cutting out of the section on internal earth fault is assured, even though there be a simultaneous external interphase fault.